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Selenium (Se) fertilizer has a good effect on many field crops, but there are few reports on the application of Se fertilizer on citrus. We investigated the effects of 0 mg/L (CK, water treatment), 50 mg/L, 100 mg/L, 150 mg/L, and 200 mg/L sodium selenite aqueous solutions on the growth, nutrition, and fruit quality of 15-year-old citrus unshiu (Citrus reticulata Blanco cv. Succosa). The results showed that a low concentration of Se fertilizer promoted the growth and development of the citrus plan, and a high concentration of Se fertilizer was found to slightly inhibit the growth and development of the plant. Among the different treatment groups, 150 mg/L selenium fertilizer showed have the best effect on these evaluated parameters. The results thus suggest that 150 mg/L of Se fertilizer promotes the formation of chlorophyll in the leaves of the test plant and increases the longitudinal and transverse diameter of the fruits and weight of single fruit, significantly enhancing the activity of antioxidant enzymes in the leaves, promoting the absorption of nutrients in the leaves, increasing the contents of total sugar and vitamin, and decreasing the acidity in the fruits and the pericarp thickness. It also promoted the accumulation of the total selenium content in the leaves and fruits and consequently improved the quality of the fruits. These results showed that appropriate concentration of Se treatment can improve the activity of antioxidant enzymes to enhance plant stress resistance, regulate the content of sugar and acid in fruits, and improve the quality of fruits.

Fungi have been proved as promising and prolific sources of functional secondary metabolites with potent agricultural applications. In this study, 14 xanthone derivatives (1-14), including six new ones, versicones I-N (1-4, 7, 11), and a biogenetically related derivative (15), were isolated from the alga-derived fungus Aspergillus versicolor D5. Their structures were elucidated by comprehensive spectroscopic methods. Versicone L (4) exhibited a broad antifungal spectrum and prominent inhibitory effects on Botrytis cinerea at a minimum inhibitory concentration (MIC) of 152 μM, 7-fold stronger than that of the positive control, carbendazim (MIC = 1.05 × 103 μM). Dihydrosterigmatocystin (13) showed strong antifungal activity toward B. cinerea at MIC = 38.3 μM, almost 30-fold stronger than that of carbendazim. Meanwhile, 13 exhibited potent herbicidal activity toward Amaranthus retroflexus L. with an MIC of 24.5 μM, approximately 4-fold stronger than that of the positive control, glyphosate (MIC = 94.7 μM). Additionally, 13 also displayed remarkable activity against other weeds belonging to Amaranth sp. Analysis of the structure-herbicidal activity relationship indicated that the bifuranic ring played an important role in xanthone phytotoxicity and the presence of a double bond in the furan ring could decrease phytotoxicity. This study indicated that xanthones can be served as promising candidates for lead compounds of agrochemicals.

Arbuscular mycorrhizal (AM) fungi can improve plant phosphorus (P) uptake; however, information about how AM fungi affect rhizosphere organic acid and microbial activity to alleviate citrus...

The effects of combined inoculation with arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) on the growth of citrus seedlings under phosphorus deficient conditions have not been extensively studied. A pot experiment was performed to compare growth, root morphology, and other physiological variables in trifoliate orange (Poncirus trifoliata L. Raf.) seedlings that had been inoculated with AMF (Rhizophagus intraradices, Ri), PGPR (Paenibacillus mucilaginosus, Pm), or both, under three phosphate fertilizer conditions by adding 0.00, 73.41, and 220.23 mg kg−1 Ca3(PO4)2 (P0, P1, and P3, respectively) in a low available phosphorus (Olsen-P 4.96 mg kg−1) culture medium. Plant growth and nitrogen and phosphorus uptake were significantly increased by inoculation with Ri and Pm at three phosphorus levels, and combined inoculation yielded the highest efficacy, particularly at P0 level. Furthermore, combined inoculation at each phosphorus level significantly increased the colonization ratios of root length with mycorrhizal hyphae and arbuscules, rhizospheric hyphal length, and Pm populations. Root morphology traits like projected area, total volume, and total root length were also considerably improved by inoculation with Ri and Pm; however, taproot length was notably reduced by mycorrhizal inoculation. At P0 level, seedlings inoculated with a combination of Ri and Pm yielded the greatest leaf chlorophyll concentrations and fine root activity, in comparison to those had either not been inoculated at all, or inoculated with just one of them. Although malondialdehyde contents and anti-oxidative enzymes activities increased in non-inoculated seedlings at P0 level, they were significantly reduced by inoculation, particularly with Ri. At P2 level, mycorrhizal seedlings exhibited markedly higher levels of anti-oxidative enzyme activity than non-mycorrhizal seedlings. Therefore, our results suggested that the efficacy of Ri inoculation was superior to that of Pm inoculation. Furthermore, combined inoculation yielded additive effects on the growth of trifoliate orange seedlings under conditions of phosphorus deficiency.

Soil microbes are the important indicator of soil quality. For exploring Chuanminshen violaceum planting to microbial effects in tobacco soil, this paper adopted Illumina MiSeq high-throughput sequencing to research the change of bacteria and fungi at the phylum and genus in the soil. The results showed that the Ch. violaceum planting increased the biodiversity of bacteria and fungi. The influence on fungi was greater than that on bacteria. It greatly increased the sequence of fungi, it obtained 32 978 16S rDNA and 32 229 18S rDNA sequence number. There was no change of the top three phylums in bacteria, but the content changed, Proteobacteria and Acidobacteria reduced by 1.73% and 1.4% respectively, and Actinobacteria increased by 0.65%. The advantage phylum Ascomycete in tobacco reduced by 27.99% to be second advantage phylum after Ch. violaceum planting, and the second advantage phylum Basidiomycete increased by 23.69% to become the first dominant fungi. At the genus, Ch. violaceum planting changed the order of dominant genus and the abundance was also changed. Some changed largely such as uncultured Acidobacteriaceae Subgroup-1, Gemmatimonas, Subgroup-2,uncultured Nitrosomonadaceae for bacteria, norank Sordariales, norank Agaricomycetes, Phialophora for fungi. Especially the rotation increased antagonistic microbes and physiological microbes and decreased pathogenic microbes. So the Ch. violaceum planting can improve the microbe community in tobacco soil.